Hot melt adhesives, 100% solids materials which are applied to a substrate when molten and cool to harden the adhesive layer, are widely used for industrial applications.
U.S. Pat. Nos. 4,816,306 and 4,874,804 to Brady, et al., disclose that hot melt packaging adhesive compositions consisting essentially of 35 to 45% by weight of an ethylene n-butyl acrylate copolymer containing 25 to 45% by weight n-butyl acrylate and having a melt index of at least 50; 35 to 55% of a terpene phenolic tackifier; and 10 to 20% by weight of a high melting point synthetic wax provide adhesives characterized by an excellent balance of high and low temperature performance without sacrifice to its machinability or thermal stability. Further, U.S. Pat. No. 5,331,033 teaches the use of the ethylene n-butyl acrylate copolymers with petroleum hydrocarbon resins and high melting point synthetic waxes to prepare adhesives useful in packages which will be subsequently subjected to repulping operations.
Most commercially available hot melt adhesives, including those discussed above, require temperatures of 350.degree. F. or greater to ensure complete melting of all the components and also to achieve a satisfactory application viscosity. The need for such elevated temperatures is not without problems. Thus, the high temperatures increase the operators risks with respect both to burns and to inhalation of residual volatiles. Finally, the high temperatures require more energy, placing greater demands on the manufacturing facility.
It would be beneficial if hot melt adhesives could be prepared which would melt to application viscosity at lower temperatures and thus could be applied without encountering any of the previously described problems.